#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>

int main() {
    int i, t = 1, s = 0;
    for (i = 1; i <= 101; i += 2)
    {
        t = t * i;
        s = s + t;
        t = -t / i;
    }
    printf("%d\n", s);
    return 0;
}